Mobile Detector, Mobile Detecting Program, and Mobile Detecting Method

1. A mobile detector, comprising: a virtual plane image generating device which generates, on an assumption that each pixel of an input image obtained by an imaging device on a mobile corresponds to each point on a virtual plane on a real world parallel to a traveling direction of the mobile, a virtual plane image by converting the input image to an image viewed from a direction perpendicular to the virtual plane; and a mobile detecting device which relates each of points on two virtual plane images which are generated at two different times, obtains a shift amount between corresponding points, and detects a detection object mobile based on an arrangement of the points having the same shift amount, wherein the mobile detecting device determines a presence of the detection object mobile when the number of points having the same shift amount in a partial area of the virtual plane image is equal to or more than a predetermined threshold value.

2. The mobile detector as claimed in claim 1 , wherein the virtual plane is perpendicular to a road surface.

3. The mobile detector as claimed in claim 1 , wherein the partial area is being a segment area which is set along the traveling direction of the image of the detection object mobile so as to include a part of the image of the detection object mobile.

4. The mobile detector as claimed in claim 1 , further comprising a mobile passing area extracting device which detects an area in a virtual plane image, which is corresponding to an area in a plane where the detection object mobile passes, as a mobile passing area, wherein the mobile detecting device determines the presence of the detection object mobile when the number of points having the same shift amount in a partial area on the virtual plane image is equal to or more than a predetermined threshold value and one or more point having the same shift amount is detected from the mobile passing area.

5. The mobile detector as claimed in claim 1 , wherein the mobile mounting the imaging device is being a vehicle, and the detection object mobile is being another vehicle traveling on a lane neighboring to a lane where the vehicle mounting the imaging device is traveling.

6. The mobile detector as claimed in claim 1 , wherein a size of the partial area in the virtual plane image is settable according to the length of the detection object mobile.

7. A non-transitory computer readable recording medium storing a mobile detecting program causing a computer connected to an imaging device installed on a mobile to execute: a virtual plane image generating function for generating, on an assumption that each pixel of an input image obtained by an imaging device corresponds to each point on a virtual plane on a real world parallel to a traveling direction of the mobile, a virtual plane image by converting the input image to an image viewed from a direction perpendicular to the virtual plane; and a mobile detecting function for relating each of points on two virtual plane images which are generated at two different times, obtaining a shift amount between corresponding points, and detecting the detection object mobile based on an arrangement of the points having the same shift amount, wherein the presence of the detection object mobile is determined by the mobile detecting function, when the number of points having the same shift amount in a partial area of the virtual plane image is equal to or more than a predetermined threshold value.

8. The non-transitory computer readable recording medium storing the mobile detecting program as claimed in claim 7 , wherein the input image is converted, by the virtual plane image generating function, to an image viewed from a perpendicular direction to the virtual plane on the real world which is perpendicular to a road surface.

9. The non-transitory computer readable recording medium storing the mobile detecting program as claimed in claim 7 , wherein the partial area is set to be a segment area which extends along the traveling direction of the image of the detection object mobile so as to include a part of the image of the detection object mobile, by the mobile detecting function.

10. The non-transitory computer readable recording medium storing the mobile detecting program as claimed in claim 7 , causing a computer to execute an area setting function for setting a size of the partial area in the virtual plane image according to the length of the detection object mobile.

11. A mobile detecting method, comprising: taking in an image at every predetermined cycle by an imaging device installed on a mobile; generating, on an assumption that each pixel of an input image obtained by an imaging device on a mobile corresponds to each point on a virtual plane on a real world parallel to a traveling direction of the mobile, a virtual plane image by converting the input image to an image viewed from a direction perpendicular to the virtual plane; relating the points on the virtual plane image generated immediately before to the points on the virtual plane image generated currently to obtain a shift amount between corresponding points; detecting the detection object mobile based on an arrangement of the points having the same shift amount; determining the presence of the detection object mobile when the number of points having the same shift amount in a partial area on the virtual plane image is equal to or more than a predetermined threshold value.

12. The mobile detecting method as claimed in claim 11 , comprising: converting the input image to an image viewed from a direction perpendicular to the virtual plane on the real world, which is perpendicular to a road surface, when generating the virtual plane image.

13. The mobile detecting method as claimed in claim 11 , comprising: setting the partial area as a segment area which extends along the traveling direction of the image of the detection object mobile so as to include a part of the image of the detection object mobile.

14. The mobile detecting method as claimed in claim 11 , comprising: setting a size of the partial area in the virtual plane image according to the length of the detection object mobile.

15. A mobile detector, comprising: virtual plane image generating means for generating, on an assumption that each pixel of an input image obtained by an imaging device on a mobile corresponds to each point on a virtual plane on a real world parallel to a traveling direction of the mobile, a virtual plane image by converting the input image to an image viewed from a direction perpendicular to the virtual plane; and mobile detecting means for relating each of points on two virtual plane images which are generated at two different times, obtaining a shift amount between corresponding points, and detecting a detection object mobile based on an arrangement of the points having the same shift amount, wherein the mobile detecting means determines a presence of the detection object mobile when the number of points having the same shift amount in a partial area of the virtual plane image is equal to or more than a predetermined threshold value.